1. Field of the Invention
The present invention relates to novel pi-conjugated polymers that may be variously useful organic electronics materials for photoelectric transducer elements, thin-film transistor elements, light-emitting elements, etc.
2. Description of the Related Art
There have been proposed, on the basis of light-emitting properties or charge transport properties of organic materials, a wide variety of function elements such as photoelectric transducer elements, thin-film transistor elements, light-emitting elements etc. The organic materials of these elements are anticipated to bring about greatest advantages of organic materials such as lightweight, cheapness, lower production cost, flexibility, etc.
Among these function elements, various low molecular-weight materials or polymer materials have been proposed or reported for hole-transport materials of solar cells or electrophotographic photoconductors in particular; typically, the former has been demanded for higher efficiency and the latter has been demanded for high-speed printing and durability.
As for materials of light-emitting elements, a wide variety of low molecular-weight or polymer materials have been reported. It is reported in the low molecular-weight materials that various laminate structures may achieve higher efficiency and suitably controlled doping processes may improve durability. However, it is also reported that, when the products are mass of low molecular-weight materials, films tend to change their conditions gradually with time; as such, there essentially exists an inevitable problem in terms of film stability.
On the other hand, polymer materials have been vigorously investigated with respect to poly-p-phenylenevinylene (PPV) and its derivatives or polythiophenes in particular. However, these materials suffer from unsatisfactory purity and/or low fluorescence quantum yield in nature, thus high-quality light-emitting elements have not currently achieved.
In view of superior stability of polymer materials by virtue of their glassy state in nature, excellent light-emitting elements can be realized provided that polymer materials are allowed to take higher fluorescence quantum yield, thus further investigations are being conducted under this concept. For example, polymer materials with a repeated unit of arylamine are the intended ones (see U.S. Pat. No. 5,777,070, Japanese Patent Application Laid-Open (JP-A) No. 10-310635, JP-A No. 08-157575, JP-A No. 2002-515078, WO 97/09394, and Synth. Met., 84, 269 (1997)).
In addition, as for organic thin film transistor (TFT) elements, a wide variety of low molecular-weight or polymer materials have been reported. For example, such materials have been investigated as low molecular-weight materials like pentacene, phthalocyanine, fullerene, anthradithiophene, thiophene oligomers and bisdithienothiophene or polymer materials like polythiophene, polythienylenevinylene and polymers containing arylamine as a repeated unit (see JP-A No. 2005-240001).
Furthermore, polymer materials having a fluorene structure have been actively investigated (see WO 00/46321, JP-A No. 2004-339206, and Macromolecules 32, 3306 (1999)).
Although the development of polymer materials in the art has significantly enhanced their hole mobility, which being a specific property for organic electronics materials, still higher mobility is required in order to apply the polymer materials to organic FET elements in particular.
In addition, the polymer materials are necessary to be sufficiently soluble into organic solvents in order to introduce greatest advantages of the organic materials, such as inexpensive production cost, sufficient flexibility and strength, lightweight, and possibility of larger area, into electronics elements. Pi-conjugated polymers, having a specific structure of stretched conjugate, typically exhibit a rigid structure, which causes lower solubility in general. The polymer materials in the art described above are mostly difficult to be dissolved, thus various molecular designs have been tried so as to avoid the insolubility.